1. Field of the Invention
This invention relates, generally, to multi-speed bicycles. More particularly, it relates to a gear mechanism that provides easy gear changing in a coaster brake bicycle having a single drive sprocket.
2. Description of the Prior Art
Most multiple speed bicycles are of the well-known derailleur type. As is well-known, such systems include multiple drive sprockets and a complex mechanism for lifting the drive chain from one drive sprocket to another in order to change gear ratios. Thirty two problems commonly associated with derailleur systems are listed in Sloan's "New Complete Book Of All-Terrain Bicycles," and twenty nine problems associated with such systems are denoted in Glenn's "New Complete Bicycle Manual." Moreover, a degree of skill is required to properly use a derailleur system. To master such a system, an athlete must memorize a number of complex procedures; Frank Berto's "Complete Guide To Upgrading Your Bike" humorously describes different shifting patterns as "The Crossover, The Half-Step, The Alpine, The Half-Step Plus Granny, The Wide Step, The Wide Step Triple, and The Rhumba Gear." Needless to say, all of these whimsical names represent real-life techniques for accomplishing various gear changes, and serious bike riders take pride in mastering these techniques, all of which are required as a result of the inherent complexity of derailleur systems.
One early speed-changing system that eschewed the derailleur system, described in Delong's "Guide To Bicycles And Bicycling," is the now obsolete Sturmey-Archer three speed system that includes a planetary gear system built into the rear axle. Delong describes a number of other systems as well.
A more recent entry in the nonderailleur market is the Shimano four speed or seven speed rear axle design; it represents a major advance over other rear wheel drive systems. Both the Shimano and Sturmey-Archer contributions to the art employ or employed a single control knob.
However, the art still lacks an inexpensive, simple-in-structure, reliable, multi-speed, single drive sprocket system with easy to operate gear changing means. The ideal system would include a dial and pointer mounted on a handle bar that would enable gear changing simply by turning the pointer on the dial; it would not make any skill demands on the rider as do the derailleur systems.
In view of the art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in this art how the ideal system could be provided.